32.5 Readline vi Mode

While the Readline library does not have a full set of vi
editing functions, it does contain enough to allow simple editing
of the line. The Readline vi mode behaves as specified in
the posix standard.

In order to switch interactively between emacs and vi
editing modes, use the command M-C-j (bound to emacs-editing-mode
when in vi mode and to vi-editing-mode in emacs mode).
The Readline default is emacs mode.

When you enter a line in vi mode, you are already placed in
`insertion' mode, as if you had typed an ‘i’. Pressing <ESC>
switches you into `command' mode, where you can edit the text of the
line with the standard vi movement keys, move to previous
history lines with ‘k’ and subsequent lines with ‘j’, and
so forth.